The regulation of gene expression by neurotransmitters and neuropeptides begins with the binding of ligands to specific membrane receptors. The overall goal of this Program is to understand the pathways used by receptor-activated second messenger systems to produce changes in gene expression. The first specific aim is to identify and characterize pathways that mediate signal transduction events important for cell growth and differentiation. These studies examine pathways involved in Drosophila embryogenesis and thyroid follicular cell growth. The second goal addresses how the seemingly ubiquitous CAMP second messenger pathway produces distinct patterns of biological effects. These studies focus on the mechanisms involved in the intracellular targeting of protein kinase A and the multifunctonal character of the CAMP-regulated enhancer. The third goal addresses how changes in intracellular calcium modulates expression of specific target genes. Core facilities provide support instrumentation, and reagents that insure the efficient accomplishment of each of these aims. These shared facilities include tissue culture, peptide synthesis and sequencing, antibody production, and administrative cores.